Device for controlling at least one valve in an internal combustion engine

ABSTRACT

A gas valve actuation device for an internal combustion engine includes a first arrangement for actuating two gas valves in a first lift event, a second arrangement for selectively actuating a first one of the two gas valves in a second lift event, a fluid circuit for controlling actuation of the first gas valve in the second lift event, wherein the fluid circuit includes a first fluid circuit valve which is arranged to be controlled by the first actuation arrangement.

BACKGROUND AND SUMMARY

The invention relates to an engine valve actuation device, especiallyfor actuating poppet valves. The engine valve actuation device may bearranged to evacuate exhaust gases from a combustion cylinder or supplyintake gas (air plus maybe EGR) to the combustion cylinder.

The invention can be applied in heavy-duty vehicles, such as trucks,buses and construction equipment. Although the invention will bedescribed with respect to a truck, the invention is not restricted tothis particular vehicle, but may also be used in other vehicles such aspassenger cars, buses and construction equipment. Further, the inventionwill be described with examples to evacuate exhaust gases from acombustion cylinder, but may alternatively be used to supply intake gas(air plus maybe EGR).

Internal combustion engines typically use either a mechanical,electrical, or hydro-mechanical valve actuation system to actuate theengine valves. These systems may include a combination of camshafts,rocker arms and push rods that are driven by the engine's crankshaftrotation. When a camshaft is used to actuate the engine valves, thetiming of the valve actuation may be fixed by the size and location ofthe lobes on the camshaft. As a complementary device, a cam phaser mightbe used for changing phase angle between engine crankshaft and enginecamshaft.

For each 360 degree rotation of the camshaft, the engine completes afull cycle made up of four strokes (i.e., expansion, exhaust, intake,and compression). Both the intake and exhaust valves may be closed, andremain closed, during most of the expansion stroke wherein the piston istraveling away from the cylinder head (i.e., the volume between thecylinder head and the piston head is increasing). During positive poweroperation, fuel is burned during the expansion stroke and positive poweris delivered by the engine. The expansion stroke ends at the bottom deadcenter point, at which time the piston reverses direction and theexhaust valve may be opened for a main exhaust event. A lobe on thecamshaft may be synchronized to open the exhaust valve for the mainexhaust event as the piston travels upward and forces combustion gasesout of the cylinder. Near the end of the exhaust stroke, another lobe onthe camshaft may open the intake valve for the main intake event atwhich time the piston travels away from the cylinder head. The intakevalve closes and the intake stroke ends when the piston is near bottomdead center. Both the intake and exhaust valves are closed as the pistonagain travels upward for the compression stroke.

The above-referenced main exhaust valve event is required for positivepower operation of an internal combustion engine. Additional auxiliaryvalve events. While not required, may be desirable. For example, it maybe desirable to actuate the exhaust valves for compression-releaseengine braking, bleeder engine braking, exhaust gas recirculation (EGR),brake gas recirculation (BGR), or other auxiliary valve events.

With respect to auxiliary valve events, flow control of exhaust gasthrough an internal combustion engine has been used in order to providevehicle engine braking. Generally, engine braking systems may controlthe flow of exhaust gas to incorporate the principles ofcompression-release type braking, exhaust gas recirculation, exhaustpressure regulation, and/or bleeder type braking.

According to a known technology, the valve train mechanism provides foropening of two exhaust valves during a main valve lift event and openingof only one of said exhaust valves during a secondary lift event such asfor engine braking. During decompression, there may be large forces inthe valve train and by opening only one of the exhaust valves the threesmay be reduced to half. A first rocker arm may be arranged for the mainlift event used both during positive and negative power and a secondrocker arm may be arranged for the secondary lift event. The firstrocker arm may be arranged to actuate both exhaust valves simultaneouslyvia a valve bridge. The second rocker arm may be arranged to actuate asingle one of said exhaust valves via a sliding pin arranged in a borein the valve bridge.

WO2010/126479 discloses system for actuating an engine valve. The systemincludes a rocker arm shaft having a control fluid supply passage and anexhaust rocker arm pivotally mounted on the rocker arm shaft. A cam forimparting main exhaust valve actuation to the exhaust rocker armcontacts a cam roller associated with the exhaust rocker arm. A valvebridge is disposed between the exhaust rocker arm and first and secondengine valves. A sliding pin is provided in the valve bridge, saidsliding pin contacting the first engine valve. An engine braking rockerarm is pivotally mounted on the rocker arm shaft adjacent to the exhaustrocker arm. The engine braking rocker arm has a central opening, ahydraulic passage connecting the central opening with a control valve,and a fluid passage connecting the control valve with an actuator pistonassembly. The actuator piston assembly includes an actuator pistonadapted to contact the sliding pin during engine braking operation. Acam is provided for imparting engine braking actuation to the enginebraking rocker arm. A plate is fastened to a back end of the enginebraking rocker arm, and a spring biases the plate and the engine brakingrocker arm into contact with the cam.

One problem with WO2010/126479 is that the engine braking operation isdependent on conditions like thermal elongation (dependent on an engineoperational state or temperature), tolerances during manual lash settingor wear in valve train. More specifically, the valve lash adjustment iscontrolled by a piston in the actuator piston assembly, which piston hasa set stroke, wherein the piston may thereby reduce a lash space todifferent extents dependent on the above conditions. This in turn has animpact on the degree of activation of the cam lobe for the enginebraking operation.

Both EP 2 677 127 A1 and U.S. Pat. No. 6,253,730 B1 disclose rocker armswith control valves, which control valves are reset valves for allowingflow forward or emptying a hydraulic chamber behind a slave piston. EP 0974 740 A2 discloses a fluid circuit valve which moves with the pistonmovement and indirectly with the rocker arm. There is however noindication of die nature of these movements.

It is desirable to provide an engine valve actuation device, whichcreates conditions for achieving engine braking in a robust way.

According to an aspect of the invention, a gas valve actuation devicefor an internal combustion engine comprises

a first means for actuating two gas valves in a first lift event,

a second means for selectively actuating a first one of said two gasvalves in a second lift event,

a fluid circuit for controlling actuation of said first gas valve in thesecond lift event,

characterized in that the fluid circuit comprises a first fluid circuitvalve, which is arranged to be controlled by the first actuation means.

This creates conditions for opening and closing the first fluid circuitvalve depending on the state or position of the first actuation means.This, in turn creates conditions for achieving an exact positioning ofthe second actuation means in an engaged state regardless of conditionslike the elongation (dependent on an engine operational state ortemperature) tolerances during manual lash setting or wear in valvetrain. This in turn creates conditions for a uniform engine brakingoperation regardless of the conditions. In other words, it createsconditions for adjusting the lash to zero in between main lift event anddecompression bump event. More specifically, the first fluid circuitvalve in the fluid circuit may be arranged between a fluid supply portand an actuator piston for actuating the first one of said two gasvalves and in such a way that the first fluid circuit valve is adaptedto block a communication between the fluid supply port and the actuatorpiston when the first fluid circuit valve is actuated by the firstactuation means. In other words, by arranging the first fluid circuitvalve in such a way that it is controlled with regard to opening andclosing the fluid circuit by the first actuation means, a robust way ofcontrolling the second lift event is achieved. According to one example,the first fluid circuit valve is directly controlled by the firstactuation means.

According to one example, the fluid circuit is formed by a hydrauliccircuit, comprising a hydraulic fluid, such as oil.

According to a further example, the first actuation means is adapted foractuating the two gas valves simultaneously in the first lift event.According to a further example, the second actuation means is adaptedfor actuating only the first one of said two gas valves in the secondlift event.

According to a further example, each one of the first actuation meansand the second actuation means comprises a mechanism or linkage foractuating the two gas valves in the first lift event and the second liftevent, respectively.

According to one embodiment, the first fluid circuit valve is arrangedto be open when the two gas valves are not actuated for the first liftevent and closed when the two gas valves are actuated for the first liftevent. This, in turn creates conditions for achieving an exactpositioning of the second actuation means in an engaged state regardlessof the conditions mentioned above. This in turn creates conditions for auniform engine braking operation irrespective of the conditions.

According to one example, the first fluid circuit valve is arranged tobe open only when the two gas valves are not actuated for the first liftevent.

According to a further embodiment, the second actuation means comprisesthe fluid circuit. In other words, at least a part of the fluid circuitis incorporated in the second actuation means. According to one example,the second actuation means is formed by at least one body and fluidlines of the fluid circuit are arranged inside of the body.

According to a further embodiment, the first actuation means comprises afirst rocker arm for actuating the two gas valves in the first liftevent, and the second means comprises a second rocker arm for actuatingthe first one of said two gas valves in the second lift event.

According to one example, the second rocker arm is arranged adjacent thefirst rocker arm. Further, each one of the first rocker arm and thesecond rocker arm are arranged to pivot around a pivot axis. Accordingto a further example, each one of the first rocker arm and the secondrocker arm comprises a through hole for receiving a rocker arm shaft,around which the rocker arms are pivotally arranged.

According to a further embodiment, the first fluid circuit valvecomprises a moveably arranged control member, which is arranged in sucha way in relation to the first rocker arm that it may be moved by amovement of the first rocker arm for opening and closing the valve. Thearrangement of the control member relative to the first rocker armcreates further conditions for securing a robust control of the gasvalve actuation.

According to one example, the control member is moveable betweendifferent positions effecting a fluid flow in the hydraulic circuit todifferent extents.

According to a further embodiment, the control member is adapted toengage with the first rocker arm.

According to a further embodiment, the control member is moveablyarranged in the second rocker arm. This is a space efficient way ofsecuring a robust control of the gas valve actuation.

According to a further embodiment, the control member is moveablyarranged in a direction substantially in parallel with a movementdirection of the first rocker arm during the first lift event.

According to one example, the first rocker arm is adapted to pivotaround a pivot axis defined by a centre axis of a rocker arm shaft.According to a further example, the control member is adapted to performa linear movement back and forth. Depending on the arrangement of thecontrol member, there may be a relative movement between the contactpoints of the rocker arm shaft and the control member. The device may beadapted to reduce any negative effects of this relative movement, suchas designing the first rocker arm and/or the control member for allowingthe relative movement and/or arranging the control member in a part thatis adapted for performing a pivoting movement similar to the firstrocker arm. This pivot part may be constituted by the second rocker arm.

According to a further embodiment, the control member comprises a firstcontact surface at a first end and wherein the first contact surface isadapted to engage with a corresponding contact surface of the firstrocker arm. According to one example, the control member and the firstrocker arm are adapted for a direct engagement with each other via thecontact surfaces. This creates conditions for securing a robust controlof the gas valve actuation.

According to a further embodiment, the control member is slidablyarranged in a bore. Preferably, the control member is formed by acylindrical body having an axis defining the sliding direction.According to one example, the control member is adapted for a linearmovement back and forth in said bore.

According to a further embodiment, the valve comprises a spring-biasedpart adapted to control fluid flow in the fluid circuit, and wherein thecontrol member is arranged to actuate the spring-biased part.

According to one example, the spring-biased part is formed by a ball,which is adapted to be arranged in a sear being provided with a port fora fluid communication line of the fluid circuit, wherein the spring isadapted to urge the part to a closed position, wherein the ball isseated in the seat covering the port. Further, the control member isarranged to move the spring-biased part away from the seat and therebyallowing fluid communication via the port.

According to a further embodiment, the control member comprises a secondcontact surface at a second end opposite the first end and wherein thesecond contact surface is arranged to engage with the spring-biasedpart.

According to a further embodiment, the fluid circuit comprises a pistonfor controlling said single one of said two gas valves in the secondlift event. According to one example, the piston is spring-biased,wherein the spring is adapted to urge the piston to a retractedposition. According to one example, the first fluid circuit valve isarranged to control fluid supply to the piston. According to oneexample, the piston is arranged on the second rocker arm.

According to a further embodiment, the device comprises a rocker armshaft and wherein the second rocker arm is pivotally arranged on saidshaft. According to one example, the first rocker arm is pivotallyarranged on the same rocker arm shaft as the second rocker arm.

According to a further development of the last mentioned embodiment, therocker arm shaft comprises a fluid supply passage adapted to providefluid to the fluid circuit.

According to a further embodiment, the fluid circuit comprises a checkvalve for preventing a reverse fluid flow in the hydraulic circuit andwherein the check valve is arranged in series with the first fluidcircuit valve.

According to a further embodiment, the device comprises a camshaftarrangement provided with a first cam adapted for actuating the firstrocker arm for the first lift event and second cam adapted for actuatingthe second rocker arm for the second lift event.

The cam has an external profile, designed for its associated lift event.More specifically, the cam profile has a non-circular shape. Accordingto one example, each cam comprises a first circumferential portionhaving a circular shape (a base circle) and a second circumferentialportion with a larger radial extension than the first circumferentialportion. The second circumferential portion may be formed by at leastone projection, such as a bump or lobe. According to a furtherembodiment, the first fluid circuit valve is arranged to be open whenthe first rocker arm is following a base circle of the cam and closedwhen the first rocker arm is following the lobe of the first cam.

According to a further embodiment, the first rocker arm comprises acontact portion adapted to engage the control member.

According to a further development of the last mentioned embodiment, thefirst rocker arm has a main extension direction in a transversedirection in relation to a rotational axis of the camshaft arrangement,wherein the first rocker arm comprises a boss projecting in a transversedirection in relation to the main extension direction and wherein theboss comprises the contact portion.

According to a further embodiment, the two gas valves are exhaustvalves.

According to a further embodiment, the device comprises a valve bridgeextending between the two gas valves for actuating both gas valves inthe first lift event and wherein the first rocker arm is adapted foractuating the two gas valves via the valve bridge.

According to a further development of the last mentioned embodiment, thevalve bridge comprises an opening in register with the first one of saidtwo gas valves, wherein the device comprises a pin slidably arranged insaid opening and wherein the second rocker arm is adapted forselectively actuating the first one of the two gas valves via thesliding pin.

The invention is further related to an internal combustion enginecomprising a cylinder provided with two intake valves and two exhaustvalves and an engine valve actuation device according to any precedingembodiment for actuating either to two intake valves or the two exhaustvalves.

Further advantages and advantageous features of the invention aredisclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detaileddescription of embodiments of the invention cited as examples.

In the drawings:

FIG. 1 shows a vehicle in the form of a truck in a partly cut side view,

FIG. 2 is a schematic perspective view of a first embodiment of anengine for the truck in FIG. 1,

FIG. 3 discloses a schematic perspective view of a gas valve actuationdevice from a camshaft side in the first embodiment of an engineaccording to FIG. 2,

FIG. 4 discloses a view from above of the gas valve actuation deviceaccording to FIG. 3,

FIG. 5 discloses a cut view of the gas valve actuation device accordingto FIG. 3 along the line A-A indicated in FIG. 4,

FIG. 6 discloses a cut view of the gas valve actuation device accordingto FIG. 3 along the line B-B indicated in FIG. 4,

FIG. 7 discloses a schematic perspective view of the gas valve actuationdevice according to FIG. 3 from a gas valve side,

FIG. 8 discloses a side view of the gas valve actuation device accordingto FIG. 7, and

FIG. 9 discloses a valve lift diagram for the gas valve actuation deviceaccording to FIG. 3.

DETAILED DESCRIPTION

FIG. 1 shows a vehicle in the form of a truck 1 in a partly cut sideview. The truck 1 comprises an internal combustion engine 2 in the formof a diesel engine.

FIG. 2 is a schematic perspective view of a first embodiment of theengine 2. The engine 2 comprises at least one cylinder 3 and in theshown example a plurality of cylinders. More specifically, the engine 2comprises four cylinders in the shown example. However, the engine maybe provided with any number of cylinders, such as six cylinders. Theengine 2 comprises a cylinder 3 provided with at least one intake valveand at least one exhaust valve 4, 5. More specifically, the cylinder 3is provided with two intake valves and two exhaust valves 4,5. Further,the engine 2 comprises a crankshaft 6. The crankshaft 6 is connected toa piston 7 in the cylinder 3 via a connecting rod 8 for transmitting adownward motion of the piston to a rotating motion of the crankshaft.Further, the engine 2 comprises a valve actuation device 100. The enginegas valves referenced constitute poppet-type valves that are used tocontrol communication between the combustion chambers (e.g., cylinders)the engine and aspirating (e.g., intake and exhaust) manifolds. Whilethe valve actuation device 100 may be used potentially for intake valveactuation, the remainder of this description describes use of the devicefor exhaust valve actuation.

The valve actuation device 100 comprises a camshaft 102. The camshaft102 is driven by the crankshaft rotation via a transmission (not shown).The valve actuation device 100 further comprises a rocker arm shaft 104in parallel with the camshaft 102. The rocker arm shaft 104 isstationary (non-rotating).

Turning now to FIG. 3, The valve actuation device 100 comprises a firstmeans 106 for actuating the two gas valves 4,5 in a first lift event anda second means 108 for selectively actuating a first one 5 of said twogas valves in a second lift event. The first means 106 is adapted foractuating the two gas valves 4,5 simultaneously in the first lift event.The first means 106 comprises a first rocker arm 110 for actuating thetwo gas valves 4,5 in the first lift event and the second means 108comprises a second rocker arm 112 for selectively actuating the firstone 5 of said two gas valves in the second lift event. The two rockerarms 110,112 are adjacent each other and pivotally disposed on saidrocker arm shaft 104.

The first rocker arm 110 forms an exhaust rocker arm and the secondrocker arm 112 forms an engine braking rocker arm. The rocker arms110,112 may be pivoted about the rocker arm shaft 104 as a result ofmotion imparted to them by the camshaft 102 or some other motionimparting device, such as a push tube.

Turning now also to FIG. 7, the exhaust rocker arm 110 is adapted toactuate the exhaust valves 4,5, by contacting them through a valvebridge 114. The exhaust rocker arm 110 may be pivoted by rotation of acam 116 rigidly attached to or formed in one-piece with the cam shaft102. The cam 116 having a bump or lobe 117 on it which contacts a earnroller 118 provided mounted on a shaft 119 provided at one end of theexhaust rocker arm 110.

The engine braking rocker arm 112 may be pivoted by rotation of a cam120 rigidly attached to or formed in one-piece with the cam shaft 102.The cam 120 has at least one engine braking bump or lobe 125, 127 on it.More specifically, the cam 120 having two bumps or lobes 125,127 (seeFIG. 3) distributed in the circumferential direction of the cam 120.More specifically, the cam 120 has a base circle region, wherein thelobes 125,127 projects radially from the base circle region and therebyhave a greater diametrical distance from the center of the cam ascompared with base circle region of the cam 120. The cam 120 may contacta cam roller 122 mounted on a shall 123 provided at one end of theengine braking rocker arm 112.

The engine braking rocker arm 112 is adapted to selectively actuate oneexhaust valve 5 by contacting a sliding pin 124 provided in the valvebridge 114, which in turn contacts the exhaust valve 5. Turning now alsoto FIG. 5, the sliding pin 124 is linearly moveably arranged in a bore131 extending through the valve bridge 114. The exhaust valve 5 may bebiased upward, into a closed position, towards the sliding pin 124 by avalve spring 126. The sliding pin 124 comprises a shoulder 128 adaptedto mate with a corresponding shoulder 130 in the valve bridge 114. Thebias of the valve spring 126 may cause the shoulder 128 on the slidingpin 124 to engage the mating shoulder 130 within the valve bridge 114.

The second rocker arm 112 includes a rocker shaft bore 113 extendinglaterally through a central portion of it for receiving the rocker armshaft 104.

Turning now also to FIG. 6, a first coil spring 132 is adapted to engagethe first rocker arm 110 to bias the first rocker arm 110 towards thecam 116. The spring 132 may push against a bracket 134 or other fixedelement. The spring 132 may have sufficient force to maintain the firstrocker arm 110 in contact with the cam 116 throughout the rotation ofthe cam shaft. For ease of presentation, the spring 132 is not disclosedin all figures disclosing the first embodiment.

A second coil spring 136 is adapted to engage the second rocker arm 112to bias the second rocker arm 112 towards the cam 120. The spring 136may push against a bracket 138 or other fixed element. The spring 136may have sufficient force to maintain the second rocker arm 112 incontact with the cam 120 throughout the rotation of the cam shaft. Forease of presentation, the spring 136 is not disclosed in all figuresdisclosing the first embodiment.

Turning now again to FIG. 5, the gas valve actuation device 100comprises a first fluid circuit 150 for controlling actuation of saidfirst gas valve 5 in the second lift event. The fluid circuit 150comprises a first fluid circuit valve 152, which is arranged to becontrolled by a position of the first rocker arm 110. The fluid circuit150 is funned by a hydraulic circuit, comprising a hydraulic fluid, suchas engine oil. The first fluid circuit valve 152 is arranged to be openwhen the two gas valves 4,5 are not actuated for the first lift eventand closed when the two gas valves 4,5 are actuated by the first rockerarm 110 for the first lift event. More specifically, the first fluidcircuit valve 152 is arranged to be open only when the two gas valves4,5 are not actuated for the first lift event.

The first fluid circuit valve 152 comprises a moveably arranged controlmember 180, which is arranged in such a way in relation to the firstrocker arm 110 that it may be moved by a movement of the first rockerarm 110 for opening and closing the valve 152.

The control member 180 is moveable between different positions effectinga fluid flow in the hydraulic circuit to different extents. Morespecifically, the control member 180 is adapted to engage with the firstrocker arms 110. Further, the control member 180 is moveably arranged inthe second rocker arm 112. The control member 180 is moveably arrangedin a direction substantially in parallel with a movement direction ofthe tint rocker arm 110 during the first lift event.

The control member 180 comprises a first contact surface 182 at a firstend and wherein the first contact surface is adapted to engage with acorresponding contact surface 184 of the first rocker arm 110. Morespecifically, the control member 180 is slidably arranged in a bore.Further, the control member 180 is formed by a cylindrical body.Further, the control member 180 comprises a first relatively thinelongated portion 190 and an enlarged portion 192 in one piece with theelongated portion 190. The enlarged portion 192 has a larger transverseextension than the elongated portion 190 has. The enlarged portion 192forms an axial stop and is adapted to form a radial gap in relation toan internal wall of the second rocker arm. Further, the enlarged portion192 is positioned at a distance from each end of the elongated portion190.

The first fluid circuit valve 152 comprises a spring-biased part 186adapted to control fluid flow in the fluid circuit, and wherein thecontrol member 180 is arranged to actuate the spring-biased part 186.The control member 180 comprises a second contact surface 187 at asecond end opposite the first end and wherein the second contact surface187 is arranged to engage with the spring-biased part 186. Thespring-biased part 186 is formed by a ball, which is adapted to beengaged by the upper surface 187 of the control member 180.

Further, the second rocker arm 112 comprises the fluid circuit 150. Thesecond rocker arm 112 further comprises a chamber 194 for housing theenlarged portion 192 of the control member 180.

The rocker arm shaft 104 comprises one or more internal passages such asfluid supply passage 154 for the delivery of the hydraulic fluid to thesecond rocker arm 112 mounted thereon. Specifically, the rocker armshaft 104 may include a constant fluid supply passage (not shown) and acontrol fluid supply passage. The constant fluid supply passage mayprovide lubricating fluid to one or more of the rocker arms duringengine operation.

The fluid circuit 150 comprises one or more internal passages, such ashydraulic passage 156 for the delivery of hydraulic fluid through it,which fluid is received from a port 158 to the bore 113 housing therocker arm shaft 104. The port 158 is in fluid communication with thefluid supply passage 154 in the rocker arm shall 104.

The fluid circuit 150 further comprises an actuator piston assembly 160,which is in communication, with the port 158 for engine braking valveactuation. The second rocker arm 112 includes a valve actuation endhaving the actuator piston assembly 160. The actuator piston assembly160 may include a slide-able actuator piston 162 disposed in a boreprovided in the engine braking rocker arm. A spring 164 may be providedfor biasing the actuator piston 160 upward, away from the sliding pin124, by acting on the actuator piston. The actuator piston assembly 160is adapted to engage an upper surface of the sliding pin 124 forcontrolling the second valve 5. The internal passages 156 in the secondrocker arm 112 are adapted to permit hydraulic fluid to be provided tothe first fluid circuit control valve 152 and the actuator pistonassembly 160.

The actuator piston assembly 160 comprises a safety valve 166. If thefluid pressure in the cavity above piston 162 exceeds a certain pressurep3 (p3>>p2; p3 is much larger than p2), a spring-biased body of thesafety valve 166 will, open a passage for the fluid to be evacuated outunder a valve cover.

Turning now again to the first fluid circuit valve 152, the chamber 194comprises a first port 196 on a first, upper side of the sectionreceiving the enlarged portion 192 of the control member 180. The firstport 196 is in fluid communication with the port 158 to the bore 113.The chamber 194 comprises a second port 198 on a second, lower side ofthe section receiving the enlarged portion 192 of the control member180. The second port 198 is in fluid communication with the actuatingactuator piston assembly 160.

The hydraulic fluid may be selectively supplied to the first fluidcircuit control valve 152 and the actuator piston assembly 160 under thecontrol of a solenoid valve, or other electrically controlled valve (notshown).

The fluid circuit 150 further comprises a check valve 170 arrangedbetween the first fluid circuit valve 152 and the actuator pistonassembly 160 for controlling fluid supply. More specifically, the checkvalve 170 is adapted for preventing a reverse fluid flow in thehydraulic circuit and wherein the check valve is arranged in series withthe first fluid circuit valve 152. The check valve 170 comprises twochambers 204, 206, which are in communication with each other via apassage 208. A port of the first chamber 204 is connected to the fluidsupply passage 154 via the fluid circuit line 156. Further, a port ofthe second chamber 206 is connected to the actuator piston 160. Thecheck valve 170 comprises a spring-biased body 210 provided in thesecond chamber for blocking fluid flow from the second chamber to thefirst chamber 204 via the passage 208. In other words, the spring-biasedbody 210 is adapted for preventing a reverse fluid flow in the hydrauliccircuit. The check valve 170 further comprises a control element 212,which is moveably arranged for actuating, the body 210 against thespring force and thereby allowing through flow of fluid from the firstchamber 204 to the second chamber 206 via the passage 208. The controlelement 212 comprises a first portion adapted to slidably engage with awall of the first chamber 204 and a second portion adapted to actuatethe spring-biased body 210 for opening the passage 208 for fluidthrough-flow. The second portion is, adapted, to be arranged in thepassage and has a smaller transverse extension than an inner extensionof the passage 208 for allowing a fluid through-flow in the passage 208when the spring-biased body 210 is moved away from its associated seat.The control element 212 is sensitive to fluid pressure in fluid circuitline 156. When fluid pressure is below pressure p1 a spring 214 to theright of control element 212 overcomes the force from fluid pressure andcontrol element 212 will move the spring-biased body 210 away from thepassage 208 and fluid is free to flow without restriction in bothdirections through passage 208. When fluid pressure is above pressurep2(p2>p1) fluid pressure acting on control element 212 will overcome thespring force from the spring 214 and control element 212 will be biasedin a right most position. When the control element 212 is in the rightmost position the spring-biased body 210 will seal the passage 208 forfluid return (backward) flow but still allow forward flow towards pistonassembly 160.

The first fluid circuit valve 152 is arranged to be open when the firstrocker arm 110 is following a base circle of the cam and closed when thefirst rocker arm is following the first cam lobe.

The first rocker arm 110 has a main extension direction in a transversedirection in relation to a rotational axis of the camshaft arrangement,wherein the first rocker arm 110 comprises a projection or boss 202projecting in a transverse direction in relation to the main extensiondirection and wherein the boss comprises the contact portion 184. Theprojection 202 may be formed in one-piece with the first rocker arm 110or by a separate arm rigidly attached to the first rocker arm 110.

Turning now to FIG. 9, it discloses valve lift as a function of crankangle. The external shape of the first cam 116 for exhaust valve controlis defined by a continuous line. More specifically, the lobe 117 isdefined by the line portion 117′. Further, a dotted line represents ashape of a cam for air intake valve control. The external shape of thesecond cam 120 for engine braking is defined by a point-dotted line.More specifically, the lobes 125,127 is defined by the line portions125′,127′.

In FIG. 9, L1 denotes an available lift height, for the rocker arm 110to control first fluid valve 180 while the two gas valves 4,5 areclosed.

When switching from engine power mode (piston 162 in upper mostposition) to engine brake mode the first fluid circuit valve 152 is openand fluid can flow in forward direction activating the piston assembly160 during an angle interval A1 when an fluid pressure in the fluidsupply passage 154 exceeds p2. When an engine brake mode is continuouslyactivated (the fluid pressure exceeds p2) some minor leakage of fluidmay occur from the hydraulic circuit. This minor leakage of fluid can becompensated by each cam shaft revolution with fluid flow during angleinterval A2. The result is zero lash adjustment for the second rockerarm 108 when gas valve 5 is in a closed position.

Operation in accordance with a first method embodiment, using the device100 for actuating the engine gas valves 4,5, will now be explainedduring positive power (non-engine braking) operation of the engine. Thefluid circuit 150 is then deactivated (lower pressure than p1). Withreference to FIGS. 1-9, engine operation causes the cam shaft 102 torotate. Since the cam 116 is rigidly attached to the cam shaft 102 andin contact with its associated roller 118 on the first rocker arm 110,the rotation of the cam shaft 102 causes the exhaust rocker arm 110 topivot about the rocker shaft 104 and actuate the exhaust valves 4,5 formain exhaust lift events via the valve bridge 114 in response tointeraction between the main exhaust lobe 117 on the cam 116 and theexhaust cam roller 118.

In the de-activated state, the fluid circuit 150 may be operated so asnot to continually supply low pressure hydraulic fluid to the controlfluid supply passage 154. As a result, hydraulic fluid pressure in thehydraulic passage 156 is insufficient to overcome the bias of theactuator piston control valve spring 164. The absence of any appreciablehydraulic fluid pressure in the actuator piston assembly 160 permits thespring 164 to push the actuator piston 162 into its upper most position,creating a lash space between the actuator piston and the sliding pin124. The lash space is sufficiently great to exist between the actuatorpiston 160 and the sliding pin 124 both when the cam roller 122 is incontact with the base circle portion of the cam 116 and when the camroller 122 is in contact with the cam lobes 125,127. Accordingly,throughout the rotation of the cam 120 during positive power operationof the engine, the actuator piston assembly 160 does not make contactwith the sliding pin 124, and the exhaust valve 5 is not actuated forengine braking.

Turning now to engine braking operation, when exhaust valve actuation isdesired for engine braking, the fluid pressure in the control fluidsupply passage 154 may be increased (larger pressure than p2). Increasedfluid pressure in the control fluid supply passage 154 is appliedthrough the hydraulic passage 156 to the actuator piston 162. As aresult, the actuator piston 162 may be displaced in the bore into an“engine brake on” position against the bias of the spring 164. Theactuator piston 162 may then extend downward, out of its bore, therebyeliminating the lash space between the actuator piston 162 and thesliding pin 124. As long as the fluid pressure is larger than p2 theactuator piston 162 is maintained in the “engine brake on” position. Theactuator piston 162 may be hydraulically locked by check valve 170 intothis extended position.

Thereafter, pivoting of the engine braking rocker ante 112 caused by thelobe 125 of the cam 120 pushing the cam roller 122 upward may produce anengine braking valve actuation corresponding to the cam lobe profile, ieits shape and size. The engine braking event occurs because the cam lobe125 of the cam 120 pivots the engine braking rocker arm 112, whichcauses the actuator piston (in its extended position) to push thesliding pin 124 downward, which in turn pushes the exhaust valve 5 open.When the cam 120 rotates so that the base circle portion is in contactwith the cam roller 122, there will be no gap (zero lash) between theactuator piston 162 and the sliding pin 124, which permits the exhaustvalve 5 to close.

When engine braking valve actuation is no longer desired, pressure inthe control fluid supply passage 154 may be reduced or vented, and theactuator piston 162 will return to an “engine brake off” position. Thesystem then returns to positive power operation.

It is to be understood that the present invention is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims. For example, it isappreciated that the exhaust rocker arm 110 could be implemented as anintake rocker arm, and the engine braking rocker arm 112 could be usedto provide auxiliary intake valve actuations, without departing from theintended scope of the invention. Furthermore, various embodiments of theinvention may include a means for biasing the engine braking rocker arm112 implemented using different spring orientations.

Further, the first fluid circuit valve may be situated in a positiondifferent from what has been disclosed above. For example, the firstfluid circuit valve may be positioned between the check valve 170 andthe actuator piston assembly 160. According to a further example, thefirst fluid circuit valve 152 may be positioned externally of the secondrocker arm. For example, the first fluid circuit valve may be situatedupstream of the second rocker arm in a fluid supply line in or to therocker arm shaft (it may require a separate first fluid circuit valvefor each cylinder.

Further, as a complementary device, a cam phaser might be used forchanging phase angle between the engine crankshaft and the enginecamshaft.

The invention claimed is:
 1. A gas valve actuation device for aninternal combustion engine, the gas valve actuation device comprising: afirst actuation means for actuating two gas valves in a first lift even;a second actuation means for selectively actuating a first gas valve ofthe two gas valves in a second lift event; a fluid circuit configured tocontrol the actuating of the first gas valve during the second liftevent, wherein the fluid circuit comprises a first fluid circuit valvecontrolled by the first actuation means such that the first fluidcircuit valve is closed only during the first lift event, for creatingconditions for achieving an exact positioning of the second actuationmeans in an engaged state of the second actuation means.
 2. The gasvalve actuation device according to claim 1, wherein the secondactuation means comprises the fluid circuit.
 3. The gas valve actuationdevice according to claim 1, wherein the first actuation means comprisesa first rocker arm and the second actuation means comprises a secondrocker arm.
 4. The gas valve actuation device according to claim 3,wherein the first fluid circuit valve comprises a control membermoveably arranged so as to open and close the first fluid circuit valveby a movement of the first rocker arm.
 5. The gas valve actuation deviceaccording to claim 4, wherein the control member is adapted to engagewith the first rocker arm.
 6. The gas valve actuation device accordingto claim 5, wherein the control member is configured to move in adirection substantially in parallel with a movement direction of the twogas valves during the first lift event.
 7. The gas valve actuationdevice according to claim 5, wherein the control member comprises afirst end including a first contact surface, wherein the first contactsurface is adapted to engage with a corresponding contact surface of thefirst rocker arm.
 8. The gas valve actuation device according to claim7, wherein the first fluid circuit valve comprises a spring-biased partadapted to control fluid flow in the fluid circuit, wherein the controlmember is arranged to actuate the spring-biased part, wherein thecontrol member further comprises a second end including a second contactsurface, wherein the second contact surface is arranged to engage withthe spring-biased part.
 9. The gas valve actuation device according toclaim 5, wherein the control member is slidably arranged in a bore. 10.The gas valve actuation device according to claim 5, wherein the controlmember includes a cylindrical body.
 11. The gas valve actuation deviceaccording to claim 4, wherein the control member is moveably arranged inthe second rocker arm.
 12. The gas valve actuation device according toclaim 4, wherein the first fluid circuit valve comprises a spring-biasedpart adapted to control fluid flow in the fluid circuit, and wherein thecontrol member is arranged to actuate the spring-biased part.
 13. Thegas valve actuation device according to claim 4, wherein the firstrocker arm comprises a contact portion adapted to engage the controlmember.
 14. The gas valve actuation device according to claim 13,wherein the first rocker arm has a main extension directionperpendicular to a rotational axis of the camshaft arrangement, whereinthe first rocker arm comprises a boss projecting parallel to therotational axis, and wherein the boss comprises the contact portion. 15.The gas valve actuation device according to claim 3, further comprisinga rocker arm shaft, wherein the second rocker arm is pivotally arrangedon the rocker arm shaft.
 16. The gas valve actuation device according toclaim 15, wherein the rocker arm shaft comprises a fluid supply passageadapted to provide fluid to the fluid circuit.
 17. The gas valveactuation device according to claim 3, further comprising a camshaftarrangement provided with a first cam configured to actuate the firstrocker arm during the first lift event and a second cam configured toactuate the second rocker arm during the second lift event.
 18. The gasvalve actuation device according to claim 3, further comprising a valvebridge extending between the two gas valves, wherein the first rockerarm is configured to actuate the two gas valves via the valve bridge.19. The gas valve actuation device according to 3, further comprising avalve bridge extending between the two gas valves wherein the firstrocker arm is configured to actuate the two gas valves via the valvebridge, wherein the valve bridge comprises an opening aligned with thefirst gas valve, and wherein the second rocker arm is configured toselectively actuate the first gas valve via a sliding pin arranged inthe opening.
 20. The gas valve actuation device according to claim 1,wherein the fluid circuit further comprises an actuator pistonconfigured to control the first one of the two gas valves in gas valveduring the second event.
 21. The gas valve actuation device according toclaim 20, wherein the first fluid circuit valve is arranged to controlfluid supply to the actuator piston.
 22. The gas valve actuation deviceaccording to claim 1, wherein the fluid circuit further comprises acheck valve configured to prevent a reverse fluid flow in the fluidcircuit, wherein the check valve is arranged in series with the firstfluid circuit valve.
 23. The gas valve actuation device according toclaim 1, wherein the two gas valves are exhaust valves.
 24. An internalcombustion engine comprising: a cylinder provided with a gas valveactuation device according to claim 1, wherein the two gas valves aretwo intake valves or the two exhaust valves.